Einar Uggerud

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Invoking a number of theoretical levels ranging from HF/STO-3G to CCSD(T)/aug-cc-pVQZ, we have made a detailed survey of six potential energy surfaces (NH4+, NH4*, [CH3CONHCH3]H+, [CH3CONHCH3]H*, [HCONHCH2CONH2]H+, [HCONHCH2CONH2]H*). In conjunction with this, ab inito direct dynamics calculations have been conducted, tracing out several hundred reaction(More)
The literature on gas phase nucleophilic substitution reactions at aliphatic carbon has been reviewed. The emphasis has been on journal articles published in the period 1990–2001. The present review outlines our current understanding of concepts such as potential energy surfaces, structure–energy relationships, microsolvation, and dynamical and mechanistic(More)
The electronic structures and bonding patterns for a new class of radical cations, [HnE-H-H-EHn]+ (EHn=element hydride, E=element of Groups 15-18), have been investigated by applying quantum-chemical methods. All structures investigated give rise to symmetric potential energy minimum structures. We envisage clear periodic trends. The H--H bond length is(More)
The potential energy surfaces for the reaction between H2O and the protonated alcohols MeOH2+, EtOH2+, PriOH2+, and Bu(t)OH2+ have been explored by means of high level ab initio theoretical methods. Both nucleophilic substitution (SN2) and elimination (E2) pathways have been investigated. Front side (SNF) and the familiar back side (SNB) Walden inversion(More)
The unimolecular chemistry of protonated formic acid, [HCOOH]H(+), has been investigated by analyzing the fragmentation of metastable ions (MI) during flight in a sector mass spectrometer, and by proton transfer to formic acid in a Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer. High level ab initio calculations have been used to model(More)
Quantum chemical calculations (OPBE/6-311++G(d,p)) have been performed to uncover the electronic factors that govern reactivity in the prototypical S(N)Ar reaction. It was found that intrinsic nucleophilicity--expressed as the critical energy (the energy required for forming the Meisenheimer structure Ph(X)(2)(-)) in the identity substitution reaction X(-)(More)
It is experimentally challenging to directly obtain structural information of the transition state (TS), the high-energy bottleneck en route from reactants to products, for solution-phase reactions. Here, we use single-molecule experiments as well as high-level quantum chemical calculations to probe the TS of disulfide bond reduction, a bimolecular(More)
Gas-phase reactions of isomeric nitrophenide ions and p-halonitrophenide ions with acrylonitrile, methyl acrylate, and ethyl acrylate have been studied using mass spectrometry and computational methods. Depending on the structure of the α,β-unsaturated compound, formation of adducts to the carbonyl group of the acrylate (for methyl acrylate and ethyl(More)
Knowledge of mechanisms of collisional energy transfer is fundamental to many areas of chemistry and physics. During recent years, it has become possible to produce beams of molecule-ions with masses above 20,000 u [1-4]. This has permitted a range of biological important compounds to be subjected to tandem mass spectrometry (also known as mass(More)